With all other infrastructure now in place, offer X86_FEATURE_VIRT_SC_SSBD to
guests in cases where Xen thinks it has a working LEGACY_SSBD interface.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Wei Liu <wei.l...@citrix.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Brian Woods <brian.wo...@amd.com>
---
xen/arch/x86/cpuid.c | 10 ++++++++++
xen/include/public/arch-x86/cpufeatureset.h | 2 +-
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index eb86a86..4ff1ea2 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -370,6 +370,16 @@ static void __init
guest_common_feature_adjustments(uint32_t *fs)
*/
if ( host_cpuid_policy.feat.ibrsb )
__set_bit(X86_FEATURE_IBPB, fs);
+
+ /*
+ * In practice, we can offer VIRT_SC_SSBD on any hardware with legacy_ssbd
+ * or msr_spec_ctrl, but until we've got a proper split between default
+ * and max policies, avoid offering it in cases where the guest shouldn't
+ * be using it.
+ */
+ __clear_bit(X86_FEATURE_VIRT_SC_SSBD, fs);
+ if ( cpu_has_legacy_ssbd )
+ __set_bit(X86_FEATURE_VIRT_SC_SSBD, fs);
}
static void __init calculate_pv_max_policy(void)
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index 8f80195..eb298cd 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -241,7 +241,7 @@ XEN_CPUFEATURE(IBPB, 8*32+12) /*A IBPB support
only (no IBRS, used by
XEN_CPUFEATURE(AMD_IBRS, 8*32+14) /* MSR_SPEC_CTRL.IBRS available */
XEN_CPUFEATURE(AMD_STIBP, 8*32+15) /* MSR_SPEC_CTRL.STIBP available */
XEN_CPUFEATURE(AMD_SSBD, 8*32+24) /* MSR_SPEC_CTRL.SSBD available */
-XEN_CPUFEATURE(VIRT_SC_SSBD, 8*32+25) /* MSR_VIRT_SPEC_CTRL.SSBD available.
*/
+XEN_CPUFEATURE(VIRT_SC_SSBD, 8*32+25) /*A MSR_VIRT_SPEC_CTRL.SSBD available.
*/
XEN_CPUFEATURE(AMD_SSB_NO, 8*32+26) /* Hardware not vulnerable to SSB */
/* Intel-defined CPU features, CPUID level 0x00000007:0.edx, word 9 */
--
2.1.4
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